Particularly the path that runs B'ton, Devils Dyke, Crawley - all advice re limits on passability welcomed.
Is there a data base that gives info re path conditons - hardpack/gravel/paved etc. Or do I have to enquire at Sustrans?
Unless on a road or named track like the Cuckoo Trail the"off road" sections are wet, muddy single tracks with very poor surfaces.
Particularly the path that runs B'ton, Devils Dyke, Crawley - all advice re limits on passability welcomed.
Do you have any knowledge of the specific routes requested?Simply untrue.
IME the typical off-road NCN path is usually hardpacked aggregate or tarmac. I would say these are perfectly doable with say 25mm tyres. I have occasionally come across sections that are bridleway and either gravelly or muddy (eg there's a section above Avebury and the descent to Avebury itself). IME these aren't common I think there should be a some way or indicating these sections but unfortunately SFAIK there isn't.
Try google images or google maps or even google street view for pictures.
NCN paths: are they manageable on skinny tyres
Particularly the path that runs B'ton, Devils Dyke, Crawley - all advice re limits on passability welcomed.
Yep - I cycled this route in March, in a circular trip from Portsmouth, Brighton, Crawley, Woking and Guildford.
There are large sections of this route that is simply impassible on a road bike. I was on a Thorn Nomad with Marathon XRs and had issues, including giving up and returning to a road detour on two occasions.
I've ridden NCN route 20 between Brighton and Pyecombe a bunch of times. From Pyecombe you're on a cycle path alongside theA27A23, or on private roads that are classified as bridleways. I think there's a small section that isn't that well-surfaced but otherwise it's all paved or tarmac with a few tree roots but no holes. After that you're on London Road/Preston Road to get into Brighton. It's a cycle lane mostly on the road, hopping onto the pavement sometimes. The pavement is ok but you'd be all right staying on the road if you prefer.
You'll need to take a detour on a local route if you want to actually go to Devil's Dyke. Don't take 89 (South Downs Way)! Though it is pretty, so you could take 82 to Devil's Dyke and then take 89 back to Route 20 if you don't mind walking a bit.
Do you have any knowledge of the specific routes requested?
You seem to be talking about general NCN routes, Cuno was responding to the specific routes in the OP.